Caption: Alien cloud. Artwork of an alien cloud approaching Earth. In 1957 the astronomer and author Fred Hoyle wrote The Black Cloud, a science fiction book about an enormous interstellar cloud of gas that enters the solar system and threatens to destroy all life on Earth by blocking the Sun's radiation. In the story, a group of astronomers establish contact with the cloud and discover that it is an intelligent living being. In 1974, Hoyle and Chandra Wickramasinghe put forward the theory that life, in the form of prebiotic proto- cells originated in large interstellar clouds of gas. These precursors to organic life would be dispersed to new planets by comets and meteorites.